1. Field of the Invention
The present invention relates to a probe card assembly used in a probe test for a semiconductor device, and a method of manufacturing such an assembly.
2. Description of the Related Art
In the probe test for semiconductor chips, a probe is brought into contact with a wafer placed on the stage, and a test signal is sent from the tester to the chip circuit via the probe. A probe card unit comprises a great number of probes, and the unit is to be held in a card holder. The probe card unit is electrically connected to a test head via a contact ring. The card holder is formed to have a coaxial 3-stepped portion.
In the case where a wafer W is electrically measured by means of such a probe card unit, the stage is stopped at such a position that the distance between the surface of the wafer and the tip of each probe is, for example, about 100 .mu.m, and then ascended so as to bring the probes into contact with pads of a number of chips on the wafer all at once. Then, the wafer is further ascended by 80 .mu.m for overdrive so as to assure the electrical contact between each probe and pad.
Recently, in many cases, the probe test is carried out under the condition of high temperature, before the wafer is diced into chips. More specifically, the wafer is heated to, for example, about 60.degree. C.-150.degree. C. by means of a heater built in the stage, and then the wafer is tested.
When the test is performed under such a high temperature condition, the card unit and the card holder are expanded by heat, and therefore the tip level of each probe (the height position of the tip of each probe) becomes lower than the level at room temperature. If each probe is brought into contact with each electrode pad, before the temperature of each of the card unit and the card holder is stabilized with respect to the temperature of the heated wafer, or the tip level of each probe is stabilized, the tip of the probe is pressed against the surface of the wafer by a large force by the expansion of the probe card due to heat propagated from the wafer after contact.
Recently, the number of pads has been increased greatly in accordance with an increase in the degree of integration of IC chip, and the number of IC chips brought into contact collectively with probes is likely to increase. The number of probes, in some cases, reaches as many as, for example, 1500. If a probe is pressed against a pad with a force larger than a predetermined load, the load applied on the stage from all the probes becomes so large that bearings of the mechanism for actuating the stage are deformed, thereby inclining the stage. As a result, some of the probes are disconnected from the respective pads, creating contact errors, and an accurate measurement cannot be conducted. Further, some probes can be damaged by deformation, and some IC chips may be damaged due to excess overdrive.